Electric power steering apparatus

Abstract

Electric power steering apparatus includes an electric motor for producing steering assist torque corresponding to steering torque applied to a steering system, and a worm gear mechanism for transmitting the steering assist torque to the steering system. The worm of the worm gear mechanism has a pressure angle greater than a pressure angle of the worm wheel, so as to reduce an actual meshing pitch circle diameter of the worm in the worm gear mechanism.

1. An electric power steering apparatus comprising:
 a steering system; 
 an electric motor for producing steering assist torque corresponding to steering torque applied to said steering system; and 
 a worm gear mechanism for transmitting the steering assist torque to said steering system, 
 wherein said worm gear mechanism includes a worm operatively connected to said electric motor and a worm wheel operatively connected to said steering system and meshing with said worm, and said worm has a pressure angle greater than a pressure angle of said worm wheel. 
 
   
   
     2. An electric power steering apparatus comprising:
 a steering system including a rack and pinion assembly; 
 an electric motor producing steering assist torque corresponding to steering torque applied to said steering system; and 
 a worm gear mechanism for transmitting the steering assist torque to said steering system, 
 wherein said worm gear mechanism includes a worm operatively connected to said electric motor and a worm wheel operatively connected to said steering system and meshing with said worm, and said worm is a single-thread worm, 
 wherein said worm is made of metal while said worm is made of resin, and wherein said worm wheel has a tooth thickness greater than a tooth height. 
 
   
   
     3. An electric power steering apparatus comprising:
 a steering system including a rack and pinion assembly; 
 an electric motor producing steering assist torque corresponding to steering torque applied to said steering system; and 
 a worm gear mechanism transmitting the steering assist torque to said steering system, 
 wherein said worm gear mechanism includes a worm operatively connected to said electric motor and a worm wheel operatively connected to said steering system and meshing with said worm, and said worm is a single-thread worm, 
 wherein said worm has a pressure angle greater than a pressure angle of said worm wheel.